Fluids such as water emulsifiable and water soluble metalworking lubricants are subject to attack by bacteria, fungi, yeasts, molds, and other microbes which tend to destroy the fluid's active ingredients and degrade the performance of the fluid.
In order to control such microbial attack, it is necessary to add a microbicide to the fluid.
Heretofore, such microbicides were added manually, by "tea-bag" type packets, or by gravity-activated devices.
In a manual application, the microbicide fluid is merely poured into the sump containing the metalworking fluid or lubricant at certain intervals, from about once a week to about once a month, depending upon the severity of the attack, in doses not exceeding about 0.02% by volume of the fluid. Since the microbicide is corrosive and contact therewith usually causes severe skin burns and eye damage, extreme handling precautions are necessary. Furthermore, an operator would often forget to add the microbicide to the fluid at the prescribed time intervals resulting in a rancid and foul-smelling fluid as well as a loss of metalworking effectiveness. Failure to add microbicide to the sumps due to annual plant shut-down, although only a once-year occurrence, is a problem recognized by the industry.
In the "tea-bag" packet type application, the microbicide is a dustless solid absorbed on an inert carrier and placed in a semi-permeable membrane packet which may then be suspended into the metalworking fluid like a "tea-bag". Such packets are generally safely handled, but gradually lose their effectiveness after being immersed in the fluid for several days due to the initial rapid leaching out of the microbicide, and hence become progressively less effective with the passage of time.
In "gravity-activated" devices, the liquid microbicide is permitted to drop or slowly flow into the sump containing the lubricant fluid, much like a liquid drips or flows from intravenous equipment. Since the microbicide additions are made at very low rates, dust and foreign material oftentimes cause interruption or cessation of the fluid flow. Further, a container of liquid microbicide hanging above a sump represents a continuous potential hazard to those in proximity to the container.
To overcome the abovementioned deficiencies of the prior art, I have found that the liquid microbicide may be added to a commercially available dispensing device which automatically continuously dispenses its contents at a controlled rate. The dispenser, now filled with the fluid microbicide, is simply dropped into a sump containing the metalworking fluid to be treated or preserved. The filled dispenser sinks to the bottom of the sump. As the dispenser slowly controllably feeds microbicide therefrom over a predetermined period of time, the dispenser slowly rises to the surface to float thereon as the microbicide therein approaches exhaustion or depletion. The empty or near-empty dispenser may then be retrieved for subsequent usage or discarded.
The dispenser may comprise a battery powered, electrochemical cell which, when activated, generates a gas to cause a diaphragm enclosing the cell to expand which urges a piston member in contact with the liquid microbicide to expel it through an outlet provided in the dispenser.
The rate of flow of the microbicide from the dispenser is normally controlled by the volume of gas formed by the electrochemical cell, which gas volume is dependent upon the amount of current applied to the cell. The current applied to the cell may readily be controlled by placing a resistor of desired value between the battery and cell, or, one of several resistors of varying resistance values may be selected to provide an assortment of volumes of gases to be generated.
The dispensing device used in the processes of the present invention may suitably comprise "Electro-Lube", manufactured by A.T.S. Electro-Lube Ltd. of 11-7550 River Road, Tilbury Industrial Park, Delta, British Columbia, Canada, and covered by U.S. Pat. No. 4,023,648, incorporated herein by reference. However, in order to facilitate an understanding of the present invention, pertinent portions of the specification and drawings are reproduced or modified herein.
The invention, of course, is not intended to be limited to the use of the abovementioned patented dispenser, since any suitable dispenser capable of continuously dispensing its contents may be adapted for use with the present inventive processes.